Saved Bookmarks
| 1. |
Prove that:Cos 570 .sin 510 + sin(-330) cos(-390)=0 |
| Answer» =>Cos (540°+30°) . Sin(540°-30°) +[-sin (360°-30°)] . cos(360°+30°)= cos (30°). Sin(30°) - sin (30°) . Cos (30°)=√3/2 × 1/2 - 1/2 ×√3/2=√3/4 - √3/4=0...... Hence proved. | |